Their
I think that's what you're asking for?
Basically, the quote means that this lady has lived a long, tired, and hardworking life. Her soul is at rest because she is satisfied with the life that she lives.
Based on the given sentence above, I can say that it is a compound sentence. What makes this sentence compound is that, it consists of two independent clauses and are connected by a coordinating conjunction "so". Therefore, the answer for this would be the last option: two independent clauses.